This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-30328 filed on Oct. 3, 2000.
1. Field of the Invention
The present invention relates to an automatic optical-axis adjusting device for automatically adjusting optical axes and illuminating zones of front lights of a vehicle based on a steering angle of a steering wheel.
2. Description of Related Art
A vehicle stability control (VSC) has been proposed to stabilize a running state of a vehicle. In the VSC, a steering angle of a steering wheel, wheel speeds of left and right wheels, a lateral G (gravity) and/or a yaw rate are used as vehicle information to determine whether a turning direction of the vehicle coincides with a steering direction of a steering wheel. If the turning direction of the vehicle does not coincide with the steering direction of the steering wheel, the steering wheel is determined to be under a counter steering state where the steering direction of the steering wheel is opposite to the turning direction of the vehicle, and a countermeasure is taken to stabilize the running state of the vehicle.
Furthermore, in a previously proposed swivel control operation of vehicle front lights, optical axes of the vehicle front lights are turned in the same direction as the steering direction of the steering wheel. However, in such a swivel control operation of the vehicle front lights, the optical axes of the front lights may be turned in the direction that is different from the driver""s desired sight direction under the counter steering state, so that the driver may experience an uncomfortable feeling. Thus, if a current state of the steering wheel is determined to be under the counter steering state, the swivel control of the front lights should be stopped, or alternatively the optical axes or the illuminating zones of the front lights should be returned to their initial states. This is also true when the vehicle is slipping, for example, on a wet curve road. In such a slipping state, the steering direction may not coincide with the turning direction of the vehicle.
If the various sensor signals utilized, for example, in the VSC are used to deal with the counter steering state of the steering wheel or to deal with the slipping state of the vehicle in the swivel control operation of the front lights, the number of the required signals becomes relatively large. This normally results in increase in costs, for example, for implementing the signal lines for these signals.
The present invention addresses the above disadvantage, and it is an objective of the present invention to provide an automatic optical-axis adjusting device for automatically adjusting optical axes of vehicle front lights capable of eliminating or reducing the above disadvantage.
To achieve the objective of the present invention, there is provided an automatic optical-axis adjusting device for automatically adjusting an optical axis of at least one front light of a vehicle. The automatic optical-axis adjusting device includes a steering angle measuring means for measuring a steering angle of a steering wheel of the vehicle, a wheel speed measuring means for measuring left and right wheel speeds of left and right wheels of the vehicle, respectively, a swivel control means for adjusting the optical axis of the at least one front light by turning the optical axis of the at least one front light in a right or left direction based on the steering angle measured with the steering angle measuring means, a counter steering state determining means for determining whether the steering wheel is under a counter steering state, and a swivel modifying means for stopping or modifying adjustment of the optical axis of the at least one front light through the swivel control means when the counter steering state determining means determines that the steering wheel is under the counter steering state. The steering wheel is determined to be under the counter steering state when the following two conditions are both satisfied: (I) the steering angle measured with the steering angle measuring means is equal to or greater than a predetermined angle; and (II) a steering direction of the steering wheel determined based on the steering angle does not coincide with a turning direction of the vehicle estimated based on a difference between the left wheel speed and the right wheel speed measured with the wheel speed measuring means.
Also, to achieve the objective of the present invention, there is also provided an automatic optical-axis adjusting device for automatically adjusting an optical axis of at least one front light of a vehicle. The automatic optical-axis adjusting device includes a steering angle measuring means for measuring a steering angle of a steering wheel of the vehicle, a wheel speed measuring means for measuring left and right wheel speeds of left and right wheels of the vehicle, respectively, a swivel control means for adjusting the optical axis of the at least one front light by turning the optical axis of the at least one front light in a right or left direction based on the steering angle measured with the steering angle measuring means, a slipping state determining means for determining whether the vehicle is under a slipping state, and a swivel modifying means for stopping or modifying adjustment of the optical axis of the at least one front light through the swivel control means when the slipping state determining means determines that the vehicle is under the slipping state. The vehicle is determined to be under the slipping state when the following two conditions are both satisfied: (I) the steering angle measured with the steering angle measuring means is equal to or greater than a predetermined angle; and (II) an absolute value of a change per unit time of a difference between the left wheel speed and the right wheel speed measured with the wheel speed measuring means is equal to or greater than a predetermined value.